1. Field of the Invention
The present invention relates to an apparatus for quenching a metallic material, and more particularly to a quenching apparatus capable of improving strength, hardness and dimension preciseness of a metallic material such as a mechanical component, and thereby diminishing wear and corrosion of the surface of the metallic material.
2. Description of the Related Art
In a quenching method, metallic material may be heated by an electric furnace, a gas furnace, a vacuum furnace, a fire furnace, or an induction furnace and is then cooled by a coolant such as gas, water, oil, or a polymer. The performance of a hardened metallic material depends on atmosphere such as cooling velocity, cooling temperature, or cooling pattern based on velocity and temperature.
In order to increase cooling velocity, the coolant in which a metallic material is soaked is mixed, or the coolant is sprayed on a metallic material from a jet nozzle. Apart from this, molten salt, molten tin, or molten lead, which is not boiled in high temperature, may cool a metallic material rapidly.
It is said that cooling a metallic material uniformly and rapidly is important to improve the characteristics thereof. However, if the temperature exceeds the boiling points of the above-mentioned coolants, these coolants boil and generate a vapor film on a portion of a metallic material. Additionally, the temperature of the portion cannot decrease rapidly. Thereby, processed metallic material has surface areas that have large temperature differences.
Specifically, if a metallic material heated to 800xc2x0 C. is hardened by water, oil, or a polymer, a vapor film is generated on the surface of the metallic material at a temperature more than 550xc2x0 C. This decreases the cooling velocity of the metallic material, because the cooling velocity is developed, according to experiments, when the vapor film vanishes in a low temperature.
Furthermore, a generated vapor film vanishes gradually from edge portions of a metallic material. Thus, vapor films are generated in some portions and are not generated in other portions, and the temperature differences thereof are known to be approximately 200xc2x0 C. to 300xc2x0 C.
According to the temperature differences, thermal shrinkage occurs in the metallic material, and the metallic material deforms, cracks, bends, or distorts. This phenomenon can be seen especially when employing water for quenching.
In order to overcome this problem in the water quenching, gas, oil, or a polymer is usually chosen. However, cooling velocity cannot be increased enough when using gas, and the obtained hardness of a metallic material is relatively low. In the case of using oil or a polymer, deformation, cracking, bending, and distortion are avoided in comparison with the case of using water. However, this improvement is not enough, and the cooling velocity is not increased enough. Further, the residual compressive stress on the surface of a hardened material declines in comparison with the water quenching, and sometimes a residual tensile stress appears, thereby decreasing the fatigue strength.
Molten salt does not generate vapor films. However, the high temperature condition for utilizing molten salt requires effort for quenching, and the handling of molten salt burdens the environment. Similarly, when substituting tin or lead, the process temperature has to be more than the melting point thereof, which also requires effort for quenching, and such a heavy metal is also treated carefully to protect the environmental reason.
The present invention has been made in view of the above-mentioned circumstances and is intended to solve the above-mentioned problems. In particular, one purpose of the present invention is to provide an apparatus for quenching a metallic material capable of restraining deformation, cracking, bending, and distortion of the metallic material to be hardened, and thereby diminishing wear and corrosion of the metallic material.
Additional purposes and advantages of the invention will be apparent to persons skilled in this field from the following description, or may be learned by practice of the invention.
The present invention provides an apparatus for quenching a metallic material, including: a heater that heats the metallic material; a liquid metal sodium chamber in which a liquid metal sodium is supplied, and the metallic material is cooled to a first temperature in the liquid metal sodium; an inert gas chamber in which an inert gas is supplied, and the metallic material is cooled to a second temperature in the inert gas; and a remover that removes a liquid metal sodium on the metallic material.
The liquid metal sodium may further include a liquid metal sodium potassium or a liquid metal sodium lithium.
The heater may be disposed in a heating furnace. The heating furnace may include a carburization quenching furnace, an induction furnace, or the like. The heater may heat the metallic material approximately to more than 700xc2x0 C.
The first temperature may be approximately 100xc2x0 C, and the second temperature may be room temperature. The first temperature may exist between 100xc2x0 C. and 250xc2x0 C. The first temperature may also exist between 150xc2x0 C. and 200xc2x0 C.
The heater may include a liquid metal sodium or a liquid metal lithium for heating the metallic material.
An inert gas may be supplied to the liquid metal sodium chamber.
The remover may include a liquid metal sodium removal chamber. An inert gas may be supplied to the liquid metal sodium removal chamber.
The remover may include a water. A water may be stored in which the metallic material is soaked for removing the remained liquid metal sodium on the metallic material.
The apparatus may further include a liquid metal sodium circulating line that circulates the liquid metal sodium supplied to the liquid metal sodium chamber. The liquid metal sodium circulating line may include a circulating pump.
The apparatus may further comprise a temperature controller that keeps the temperature of the liquid metal sodium supplied to the liquid metal sodium chamber constant.
The apparatus may further comprise an impurity remover that removes an impurity in the liquid metal sodium supplied to the liquid metal sodium chamber.
The apparatus may further comprise a mixer that mixes the liquid metal sodium supplied in the liquid metal sodium chamber.
The apparatus may further comprise a mixer that mixes the inert gas supplied in the liquid metal sodium removal chamber.
The apparatus may further comprise a mixer that mixes the inert gas supplied in the liquid metal sodium removal chamber.
The apparatus may further comprise a shield that avoids air contacting the liquid metal sodium.
The apparatus may further comprise a transporter that transports the metallic material for the processes.
The present invention also provides an apparatus for quenching a metallic material, including: a heater at a first temperature; a first chamber downstream from the heater and containing a liquid metal sodium at a second temperature lower than the first temperature; a second chamber downstream from the first chamber and containing an inert gas at a third temperature lower than the second temperature; and a liquid metal sodium remover downstream from the second chamber.
The present invention also provides an apparatus for quenching a metallic material, including: a heater for heating the metallic material to a first temperature; a first chamber containing a liquid metal sodium at a second temperature lower than the first temperature for cooling the metallic material heated to the first temperature; a second chamber containing an inert gas at a third temperature lower than the second temperature for cooling the metallic material; and a liquid metal sodium remover for removing a liquid metal sodium from the metallic material.
Further, the present invention also provides a method of quenching a metallic material, including: heating the metallic material to a first temperature; cooling the metallic material in a liquid comprising a liquid metal sodium to a second temperature lower than the first temperature; cooling the metallic material in an inert gas to a third temperature lower than the second temperature; and removing a liquid metal sodium from the metallic material cooled to at least the third temperature.